By name: vacoal-hippocampal-memory description: "VaCoAl algebro-deterministic hippocampal memory architecture. Bridges silicon and hippocampus by connecting Vector-HaSH, TEM, and hyperdimensional computing. Use when: hippocampal memory modeling, grid-cell scaffolds, episodic memory replay, sharp-wave ripples, Vector-HaSH, Tolman-Eichenbaum Machine, hyperdimensional computing, Galois-field LFSRs, multi-hop memory replay, memory fidelity decay, STDP-like path selection, EC-CA3 pathways, dentate gyrus, compositional memory, hippocampal-entorhinal circuit."
VaCoAl: Algebro-Deterministic Hippocampal Memory Architecture
Paper Reference
- Title: Bridging Silicon and the Hippocampus: Algebro-Deterministic Memory "VaCoAl" as a Substrate for Vector-HaSH and TEM
- arXiv: 2605.15652
- Authors: Hiroyuki Chuma, Kanji Otsuka, Yoichi Sato
- Date: 2026-05-19
- Category: cs.NE (Neural and Evolutionary Computing)
Core Innovation
VaCoAl provides a shared algebraic object connecting three parallel research literatures:
- Vector-HaSH: Hippocampal-entorhinal circuit factorizes content from grid-cell scaffold
- TEM (Tolman-Eichenbaum Machine): Compositional memory via ripple-mediated replay
- Human iEEG findings: Sharp-wave ripples gate episodic recall; multi-hop replay fidelity decays multiplicatively
Key Components
1. Galois-Field Diffusion Substrate
- Deterministic Galois-field LFSRs provide quasi-orthogonal vectors
- Replaces Vector-HaSH's random scaffold-to-hippocampus projection
- Advantages: Matched second-moment statistics, stronger avalanche behavior, bit-exact reproducibility
- Architecture: Built from Linear Feedback Shift Registers over GF(2)
2. Confidence Ratio (CR) Model for Multi-Hop Replay
- CR1: Per-step confidence ratio for single-hop reactivation
- CR2: Path-integral = product of CR1 values along n-hop chain
- Models observed multiplicative decay in multi-hop replay fidelity
- First algebraically tractable model under conditional independence assumption
3. STDP-like Path Selection
Emerges from architectural demands:
- Similarity preservation
- Compositional reversibility
- Bounded-frontier search
4. Hippocampal Pathway Correspondences
VaCoAl operating regimes share architectural commitments with:
- EC → CA3: Direct entorhinal-to-CA3 pathway
- EC → DG → CA3: Dentate gyrus-mediated pathway
- Conserved across >520 Myr of evolution
Testable Predictions
- Multiplicative fidelity decay follows CR1^n form in iEEG recordings
- Ripple-locked cortical reactivation patterns match VaCoAl replay sequences
- DG elaboration in primates reflects capacity-plasticity tradeoff predicted by VaCoAl
Activation Keywords
hippocampal memory, VaCoAl, Vector-HaSH, Tolman-Eichenbaum Machine, grid cells, episodic memory, sharp-wave ripples, hyperdimensional computing, Galois field, LFSR, multi-hop replay, STDP, entorhinal cortex, CA3, dentate gyrus, compositional memory, memory fidelity decay